3.
Coat the paper with a 20% solution of silver nitrate.This creates silver nitrate
crystals. These are deposited within the fibres of the paper; not
held in by gelatin as was the case with later processes. The
amount of silver deposited in the paper was only about one tenth the
level that is found in modern prints.

3.
Lay the negative over the paper and expose to sunlight.

Fix the Image

4.
After exposure fix the image to ensure that it remains captured on the
paper. Fixing can be achieved by using:

- a concentrated solution of silver nitrate

- hyposulphite of soda
('hypo') as is used today, or

- one of the halides such as silver iodide.

The
use of sodium hyposulphite (hypo) to fix prints was known from the early
days, but Talbot continued to use his concentrated silver nitrate (salt)
solution.

The
early photographers in St Andrews also persisted with salt fixing their
prints, and had difficulty achieving successful results.

Later,
Talbot changed to using silver bromide to fix his prints.

A
more popular fixer, used by others was silver iodide. Silver
chloride and potassium bromide could also be used.

Hill
& Adamson experimented with several of these fixing solutions.

5. After fixing, wash he
print thoroughly to remove the fixer and prevent it subsequently
damaging the print. Some photographers washed their prints for 12
to 24 hours or longer, perhaps using 20 changes of water.

Blanquet- Evrard's Announcement
- 1851

The above is
a 'printing-out process'. This is the process that was normally
used.

However, Louis-Desiré
Blanquet-Evrard, in 1851 announced that it was possible to
produce prints more quickly by developing, fixing and washing, as for a
negative.

Result

Hill & Adamson's Results

The results
was a small brown image, which could be delightful when well printed,
though many early photographers had difficulty making successful salt
prints.

The success of the
process, and the amount of detail retained in the calotype
depended on many factors, including the batch of paper used.
Talbot often used Watman's Rag Paper.

Turner's Patent Tablotype paper gave excellent results in
the late 1840s and early 1850s.

Much of the paper produced today includes bleaches, or
even hypo, and so is not suitable for making calotype prints.

Fading

The
image was very delicate and liable to fade. Fading can be reduced by the
exclusion of air. e.g. when two prints have been pressed together
in a photographic album, they tend to show less fading.

Many
of Talbot's images have faded badly.

Hill
& Adamson's images have survived better, apart from fading around the
edges of some. This may be due to the care taken by Adamson in
making the prints - possibly even due to some particular aspect of
Adamson's processing. DO Hill remarked that Adamson "...
thinks he knows some things others do not."

Tones
in the Print

Tones of salted
paper prints can vary from reddish-brown to chestnut brown;
purplish brown if toned with gold chloride for greater permanence;
yellowish brown if faded.

They sometimes exhibit a lilac
tone. This is likely to occur in prints fixed with silver chloride,
and is due to incomplete removal of silver by the fixer.

They sometimes exhibit primrose
yellow tones. This is
likely to occur in iodide-fixed prints, and is due to silver chloride
having been transformed to silver iodide.

Surface of the Print

Except for those that hae been glazed or
varnished with a thin coating of albumen (so producing albumenized salt
prints), salt paper prints have a matt surface. The tones are
embedded in the fibres of the paper.

Waxed
Paper Negatives

Waxing of the negative paper
enabled more detail to be retained, and prevented the fibres of the
calotype negative being seen in the final print.

Talbot left a documentary
record of his methods for producing prints. Hill &
Adamson did not.

Museum of Edinburgh
Investigations

Experiments
have begun at the Museum of Edinburgh, carrying out non-destructive
analysis of some of Hill & Adamson's calotypes and prints looking
for the levels of silver, bromide, iodine, iron, cobalt, copper,
zink arsenic and other elements in these prints.

This
should help in determining what chemicals were likely to have been
added in the smelt during the paper-making, and what chemicals were used
by Adamson in making the his prints.

Experiments
are ongoing. It appears that Adamson appears to have experimented
with different chemicals, but no 'secret ingredient' has been found.